Methods for providing variable feature widths in a self-aligned spacer-mask patterning process

ABSTRACT

A method includes forming a first mandrel layer above a first process layer. A first implant region is formed in the first mandrel layer. The first mandrel layer is patterned to define a plurality of first mandrel elements. At least a first subset of the first mandrel elements is formed from the first mandrel layer outside the first implant region and a second subset of the first mandrel elements is formed from the first implant region. First spacers are formed on sidewalls of the plurality of first mandrel elements. The first subset of the first mandrel elements are selectively removed without removing the second subset of the first mandrel elements. The first process layer is patterned using the first spacers and the second subset of the first mandrel elements as an etch mask.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The disclosed subject matter relates generally to the fabrication ofsemiconductor devices and, more particularly, to methods for providingvariable feature widths in a self-aligned spacer-mask patterningprocess.

2. Description of the Related Art

In modern integrated circuits, minimum feature sizes, such as thechannel length of field effect transistors as defined by the criticaldimension (CD) of the gate electrode, have reached the deep sub-micronrange, thereby steadily increasing performance of these circuits interms of speed and/or power consumption and/or diversity of circuitfunctions. Existing optical lithography is capable of high-throughputprocessing, but the patterning pitch of a single optical lithographystep is limited. A challenge for lithography is to devise tools,materials and processes that can reliably, efficiently and quicklypattern structures with smaller dimensions, reduced pitch or variedpitches.

The CD of the gate electrodes, which also defines the channel length, istypically limited by the photolithography processes employed. To improvethe reliability of the patterning process, a large number of evenlyspaced lines are typically formed in a regular pattern. The width ofeach line and the pitch between lines is determined by the patterningprocess. In an exemplary self-aligned technique, referred to asself-aligned double patterning (SADP), a hard mask layer is formed abovea gate electrode material layer and a plurality of mandrel line elementsis formed above the hard mask layer. Spacers are formed on sidewalls ofthe mandrel and the mandrel is removed, leaving the spacers as an etchmask for patterning the hard mask layer. The pitch of the spacers iseffectively double that of the mandrel elements. Another technique,referred to as self-aligned quadruple patterning (SAQP), forms anotherset of spacers and removes the first set, effectively quadrupling thepitch of the mandrel elements. The patterned hard mask layer is used toetch the underlying gate electrode material layer.

In some devices, arrays of narrow gate electrodes are bounded by widerlines of gate electrode material to provide mechanical stability to thepattern for various processing steps, such as planarization andcleaning. Due to the regular nature of the spacers and the self-alignedprocess, it is inherently difficult to pattern lines with widths greaterthan the characteristic width of the patterning process, referred to asthe 1× width. The patterning of wider lines, such as those needed forhigh current capacity power rails, typically requires additional maskingand patterning steps, giving rise to increased fabrication complexityand cost. Due to the use of multiple patterning technologies, defectsmay also increase, such as overlay errors, pitch walking, hard maskprofile defects, etc.

The present application is directed to eliminating or reducing theeffects of one or more of the problems identified above.

SUMMARY OF THE INVENTION

The following presents a simplified summary of the invention in order toprovide a basic understanding of some aspects of the invention. Thissummary is not an exhaustive overview of the invention. It is notintended to identify key or critical elements of the invention or todelineate the scope of the invention. Its sole purpose is to presentsome concepts in a simplified form as a prelude to the more detaileddescription that is discussed later.

Generally, the present disclosure is directed to various methods forproviding variable feature widths in a self-aligned spacer-maskpatterning process. One illustrative method includes, among otherthings, forming a first mandrel layer above a first process layer. Afirst implant region is formed in the first mandrel layer. The firstmandrel layer is patterned to define a plurality of first mandrelelements. At least a first subset of the first mandrel elements isformed from the first mandrel layer outside the first implant region anda second subset of the first mandrel elements is formed from the firstimplant region. First spacers are formed on sidewalls of the pluralityof first mandrel elements. The first subset of the first mandrelelements are selectively removed without removing the second subset ofthe first mandrel elements. The first process layer is patterned usingthe first spacers and the second subset of the first mandrel elements asan etch mask.

Another illustrative method includes, among other things, forming alower mandrel layer above a process layer. A lower implant region isformed in the lower mandrel layer. An upper mandrel layer is formedabove the lower mandrel layer. An upper implant region is formed in theupper mandrel layer. The upper mandrel layer is patterned to define aplurality of first mandrel elements. At least a first subset of thefirst mandrel elements is formed from the upper mandrel layer outsidethe upper implant region and a second subset of the upper mandrelelements is formed from the upper implant region. First spacers areformed on sidewalls of the plurality of upper mandrel elements. Thefirst subset of the upper mandrel elements is selectively removedwithout removing the second subset of the upper mandrel elements. Thelower mandrel layer is patterned using the first spacers and the secondsubset of the upper mandrel elements as an etch mask to define aplurality of lower mandrel elements. At least a first subset of thelower mandrel elements is formed from the lower mandrel layer outsidethe lower implant region and a second subset of the lower mandrelelements is formed from the lower implant region. Second spacers areformed on sidewalls of the plurality of lower mandrel elements. Thefirst subset of the lower mandrel elements is selectively removedwithout removing the second subset of the lower mandrel elements. Theprocess layer is patterned using the second spacers and the secondsubset of the lower mandrel elements as an etch mask.

BRIEF DESCRIPTION OF THE DRAWINGS

The disclosure may be understood by reference to the followingdescription taken in conjunction with the accompanying drawings, inwhich like reference numerals identify like elements, and in which:

FIGS. 1A-1H are cross-sectional diagrams illustrating patterning of aprocess layer using a sidewall image template with a modified mandrel;

FIGS. 2A-2B are cross-sectional diagrams illustrating patterning of aprocess layer in a self-aligned quadruple patterning process using asidewall image template with a modified lower mandrel;

FIGS. 3A-3G are cross-sectional diagrams illustrating patterning of aprocess layer in a self-aligned quadruple patterning process using asidewall image template with a modified upper mandrel; and

FIGS. 4A-4G are cross-sectional diagrams illustrating patterning of aprocess layer in a self-aligned quadruple patterning process using asidewall image template with modified upper and lower mandrels.

While the subject matter disclosed herein is susceptible to variousmodifications and alternative forms, specific embodiments thereof havebeen shown by way of example in the drawings and are herein described indetail. It should be understood, however, that the description herein ofspecific embodiments is not intended to limit the invention to theparticular forms disclosed, but on the contrary, the intention is tocover all modifications, equivalents, and alternatives falling withinthe spirit and scope of the invention as defined by the appended claims.

DETAILED DESCRIPTION

Various illustrative embodiments of the invention are described below.In the interest of clarity, not all features of an actual implementationare described in this specification. It will of course be appreciatedthat in the development of any such actual embodiment, numerousimplementation-specific decisions must be made to achieve thedevelopers' specific goals, such as compliance with system-related andbusiness-related constraints, which will vary from one implementation toanother. Moreover, it will be appreciated that such a development effortmight be complex and time-consuming, but would nevertheless be a routineundertaking for those of ordinary skill in the art having the benefit ofthis disclosure.

The present subject matter will now be described with reference to theattached figures. Various structures, systems and devices areschematically depicted in the drawings for purposes of explanation onlyand so as to not obscure the present disclosure with details that arewell known to those skilled in the art. Nevertheless, the attacheddrawings are included to describe and explain illustrative examples ofthe present disclosure. The words and phrases used herein should beunderstood and interpreted to have a meaning consistent with theunderstanding of those words and phrases by those skilled in therelevant art. No special definition of a term or phrase, i.e., adefinition that is different from the ordinary and customary meaning asunderstood by those skilled in the art, is intended to be implied byconsistent usage of the term or phrase herein. To the extent that a termor phrase is intended to have a special meaning, i.e., a meaning otherthan that understood by skilled artisans, such a special definition willbe expressly set forth in the specification in a definitional mannerthat directly and unequivocally provides the special definition for theterm or phrase. The present disclosure is directed to various methodsfor providing variable feature widths in a self-aligned spacer-maskpatterning process. With reference to the attached drawings variousillustrative embodiments of the methods and devices disclosed hereinwill now be described in more detail.

FIGS. 1A-1H are cross-sectional diagrams illustrating a method forforming a semiconductor device 100 by patterning a process layer using asidewall image template with a modified mandrel. FIG. 1A illustrates thedevice 100 including a substrate 105, an isolation structure 110 (e.g.,silicon dioxide), a gate material layer 115 (e.g., amorphous silicon), afirst hard mask layer 120 (e.g., silicon nitride), a mandrel layer 125and a patterned mask layer 130 (e.g., a stack including organicpatterning layer, anti-reflective coating layer, photoresist layer,etc.). Although the example illustrates the patterning of a gatematerial layer 115, other layers may be patterned, such as a mandrellayer, an insulating material layer, etc. The substrate 105 may have avariety of configurations, such as the depicted bulk siliconconfiguration. The substrate 105 may also have a silicon-on-insulator(SOI) configuration that includes a bulk silicon layer, a buriedinsulation layer and an active layer, wherein semiconductor devices areformed in and above the active layer. The substrate 105 may be formed ofsilicon or silicon germanium or it may be made of materials other thansilicon, such as germanium. Thus, the terms “substrate” or“semiconductor substrate” should be understood to cover allsemiconducting materials and all forms of such materials. The substrate105 may have different layers.

The device 100 may include transistor devices, such as finFET transistordevices above which gate electrodes may be patterned from the gatematerial layer 115. Typically, the isolation structure 110 is formedabove a plurality of fins (not shown) and recessed to expose upper finportions while remaining in the trenches between the fins to provideisolation therebetween. For ease of illustration, the stack of layers105-130 is illustrated in a region outside the fins (e.g., gate over STIregion).

FIG. 1B illustrates the device 100 after an implantation process 135 wasperformed through the patterned mask layer 130 to define an implantregion 125M in the mandrel layer 125. In one embodiment, the mandrellayer 125 may be implanted with a dopant such as boron to define theimplant region 125M. In general, the implantation of a dopant into themandrel layer 125 modifies the etch characteristics of the implantregion 125M with respect to the remaining portions of the mandrel layer125.

FIG. 1C illustrates the device 100 after several processes wereperformed. An etch or strip process was performed to remove thepatterned mask layer 130. A deposition process was performed to form asecond hard mask layer 140 above the mandrel layer 125. Severalprocesses were performed to form a patterned mask layer 145 above thesecond hard mask layer 140 for patterning the mandrel layer 125.

FIG. 1D illustrates the device 100 after several processes wereperformed. First, an etch process was performed through the patternedmask layer 145 to pattern the hard mask layer 140. Additional etchprocesses were performed to etch the mandrel layer 125 selectively tothe hard mask layer 140 to define mandrel elements 125A, 125B from themandrel layer 125. Portions of the patterned hard mask layer 140 remainon upper surfaces of the mandrel elements 125A, 125B. The mandrelelements 125B were formed from the implant region 125M, so they havedifferent etch characteristics than the mandrel elements 125A. An etchor strip process may have been performed to remove the patterned masklayer 145, or the patterned mask layer 145 may have been be consumedduring the etching of the mandrel layer 125.

FIG. 1E illustrates the device 100 after several processes wereperformed. First, a spacer layer (e.g., silicon dioxide—not shown) wasformed above the mandrel elements and the hard mask layer 120. Then ananisotropic etch process was performed to remove portions of the spacerlayer formed on horizontal portions of the hard mask layers 120, 140 todefine spacers 150A, 150B on sidewalls of the mandrel elements 125A,125B, respectively. The remaining portions of the hard mask layer 140may be removed by tuning the etch chemistry during the spacer etch or bya subsequent etch process.

FIG. 1F illustrates the device 100 after an etch process was performedto remove the mandrel elements 125A selectively to the mandrel elements125B. Because of the presence of the implanted dopant in the mandrelelements 125B, the mandrel elements 125A may be selectively removed. Thespacers 150A define narrow mask elements, and the combined mandrelelement 125B/spacer 150B structures define wide mask elements.

FIG. 1G illustrates the device 100 after several etch processes wereperformed. First, an etch process was performed through the spacers 150Aand the combined structures formed by the spacers 150B and the mandrelelements 125B to pattern the hard mask layer 120. One or more etchprocesses were performed to remove the spacers 150A, 150B, and themandrel elements 150B. Next, an etch process was performed through thepatterned hard mask layer 120 to etch the gate material layer 115.

FIG. 1H illustrates the device 100 after an etch process was performedto remove the hard mask layer 120. The device includes short channelgate structures 115S and long channel gate structures 115L. Hence,narrow and wide patterns may be formed using the same photolithographyand self-aligned processes. Although an extra mask process is requiredto form the implant region 125M in FIG. 1B, the photolithographyconstraints for doing so are not significant and do not give rise to thealignment and pitch walking defects described above.

FIGS. 1A-1H illustrate a self-aligned double patterning (SADP) scheme.The techniques may also be employed with a self-aligned quadrature(SAQP) process which employs two mandrel layers. The modification of themandrel etch selectivity may be performed on the upper mandrel layer,the lower mandrel layer, or both mandrel layers, as illustrated below.

FIGS. 2A-2B illustrate a device 200 where the modification of themandrel etch selectivity is performed on the lower mandrel layer. InFIG. 2A, the mandrel layer 125 is a lower mandrel layer. Starting with astructure similar to that illustrated in FIG. 1C, an upper mandrel layerwas formed above the hard mask layer 140 and patterned to define uppermandrel elements 205. A spacer layer was formed and etched to definespacers 210 adjacent the upper mandrel elements 205.

FIG. 2B illustrates the device after several processes were performed totransfer the pattern defined by the spacers 210 to the mandrel layer125. An etch process was performed to remove the mandrel elements 205.An etch process was performed through the spacers 210 to pattern thehard mask layer 140. One or more etch processes were performed to removethe spacers 210. An etch process was performed through the patternedhard mask layer 140 to pattern the mandrel layer 125, defining mandrelelements 125A, 125B from the mandrel layer 125. Again, since the mandrelelements 125B were formed from the implant region 125M, so they havedifferent etch characteristics than the mandrel elements 125A. A spacerlayer (e.g., silicon dioxide—not shown) was formed above the mandrelelements 125A, 125B and the hard mask layer 120. Then an anisotropicetch process was performed to remove portions of the spacer layer formedon horizontal portions of the hard mask layer 140 to define spacers 215on sidewalls of the mandrel elements 125A, 125B, respectively.Processing may continue as described in FIGS. 1G and 1H to complete thepatterning of the gate material layer 115.

FIGS. 3A-3G illustrate a device 301 where the modification of themandrel etch selectivity is performed on the upper mandrel layer. InFIG. 3A, the mandrel layer 125 is a lower mandrel layer. An uppermandrel layer 300 was formed above the hard mask layer 140, the uppermandrel layer 300 was implanted using a patterned mask (i.e., similar tothe process shown in FIG. 1B) to define an implant region 300M, a hardmask layer 305 was formed above the upper mandrel layer 300, and apatterned mask layer 310 was formed above the hard mask layer 305.

FIG. 3B illustrates the device 301 after several processes wereperformed. First, an etch process was performed through the patternedmask layer 310 to pattern the hard mask layer 305. Additional etchprocesses were performed to etch the upper mandrel layer 300 selectivelyto the hard mask layer 305 to define mandrel elements 300A, 300B fromthe mandrel layer 300. The mandrel element 300B was formed from theimplant region 300M, so it has different etch characteristics than themandrel elements 300A. An etch or strip process may have been performedto remove the patterned mask layer 310, or the patterned mask layer 310may have been consumed during the etching of mandrel layer 300. A spacerlayer (e.g., silicon dioxide—not shown) was formed above the mandrelelements 300A, 300B and an anisotropic etch process was performed toremove portions of the spacer layer formed on horizontal portions of thehard mask layer 140 to define spacers 315A, 315B on sidewalls of themandrel elements 300A, 300B, respectively. The remaining portions of thehard mask layer 305 may be removed by tuning the etch chemistry duringthe spacer etch or by a subsequent etch process.

FIG. 3C illustrates the device 301 after an etch process was performedto remove the mandrel elements 300A selectively to the mandrel elements300B. Because of the presence of the implanted dopant in the mandrelelements 300B, the mandrel elements 300A may be selectively removed. Thespacers 315A define narrow mask elements, and the combined mandrelelement 300B/spacer 315B structures define wide mask elements.

FIG. 3D illustrates the device 301 after several etch processes wereperformed. First, an etch process was performed through the spacers 315Aand the combined structures formed by the spacers 315B and the mandrelelement 300B to pattern the hard mask layer 140. One or more etchprocesses were performed to remove the spacers 315A, 315B, and themandrel element 300B. Next, an etch process was performed through thepatterned hard mask layer 140 to etch the lower mandrel layer 125 todefine narrow mandrel elements 125A and a wide mandrel element 125B.

FIG. 3E illustrates the device 301 after several processes wereperformed. First, a spacer layer (e.g., silicon dioxide—not shown) wasformed above the mandrel elements and the hard mask layer 120. Then ananisotropic etch process was performed to remove portions of the spacerlayer formed on horizontal portions of the hard mask layers 120, 140 todefine spacers 150A, 150B on sidewalls of the mandrel elements 125A,125B, respectively. The remaining portions of the hard mask layer 140may be removed by tuning the etch chemistry during the spacer etch or bya subsequent etch process.

FIG. 3F illustrates the device 301 after an etch process was performedto remove the mandrel elements 125A, 125B. Because the implanted dopantwas not present in the mandrel element 125B, all the mandrel elements125A, 125B were removed. The spacers 150A, 150B define narrow maskelements, and the region that was occupied by the mandrel element 125Bdefines a space 320 between first and second sets 325, 330 of mandrelelements. The self-aligned process for defining the spacers 150A, 150Ballows the space 320 to be defined without any additional masking orphotolithography.

FIG. 3G illustrates the device 301 after several processes wereperformed to transfer the pattern defined by the spacers 150A, 150B tothe gate material layer 115. An etch process was performed through thespacers 150A, 150B to pattern the hard mask layer 120. One or more etchprocesses were performed to remove the spacers 150A, 150B. An etchprocess was performed through the patterned hard mask layer 120 topattern the gate material layer 115, defining short channel gatestructures 115S separated by the space 320. An etch process wasperformed to remove the patterned hard mask layer 120.

FIGS. 4A-4G illustrate a device 401 where the modification of themandrel etch selectivity is performed on both mandrel layers. In FIG.4A, the mandrel layer 125 is a lower mandrel layer. An upper mandrellayer 400 was formed above the hard mask layer 140. The lower mandrellayer 125 was implanted using a patterned mask (i.e., similar to theprocess shown in FIG. 1B) to define an implant region 125M and the uppermandrel layer 400 was implanted to define an implant region 400M. Theimplant regions 125M, 400M may be formed concurrently, or the implantregion 125M may be formed prior to forming the hard mask layer 140 andthe upper mandrel layer 400. A hard mask layer 405 was formed above theupper mandrel layer 400, and a patterned mask layer 410 was formed abovethe hard mask layer 405. In FIG. 4A, the implant regions 125M, 400M arevertically aligned and have the same width. In some embodiments, thefirst and second implant regions 125M, 400M may not be aligned, they mayhave different widths, and more than one implant region may be formed inthe respective mandrel layers 125, 400.

FIG. 4B illustrates the device 401 after several processes wereperformed. First, an etch process was performed through the patternedmask layer 410 to pattern the hard mask layer 405. Additional etchprocesses were performed to etch the upper mandrel layer 400 selectivelyto the hard mask layer 405 to define mandrel elements 400A, 400B fromthe mandrel layer 400. The mandrel element 400B was formed from theimplant region 400M, so it has different etch characteristics than themandrel elements 400A. An etch or strip process may have been performedto remove the patterned mask layer 410, or the patterned mask layer 410may have been consumed during the etching of mandrel layer 400. A spacerlayer (e.g., silicon dioxide—not shown) was formed above the mandrelelements 400A, 400B and an anisotropic etch process was performed toremove portions of the spacer layer formed on horizontal portions of thehard mask layer 140 to define spacers 415A, 415B on sidewalls of themandrel elements 400A, 400B, respectively. The remaining portions of thehard mask layer 405 may be removed by tuning the etch chemistry duringthe spacer etch or by a subsequent etch process.

FIG. 4C illustrates the device 401 after an etch process was performedto remove the mandrel elements 400A selectively to the mandrel elements400B. Because of the presence of the implanted dopant in the mandrelelements 400B, the mandrel elements 400A may be selectively removed. Thespacers 415A define narrow mask elements, and the combined mandrelelement 400B/spacer 415B structures define wide mask elements.

FIG. 4D illustrates the device 401 after several etch processes wereperformed. First, an etch process was performed through the spacers 415Aand the combined structures formed by the spacers 415B and the mandrelelement 400B to pattern the hard mask layer 140. One or more etchprocesses were performed to remove the spacers 415A, 415B, and themandrel element 400B. Next, an etch process was performed through thepatterned hard mask layer 140 to etch the lower mandrel layer 125 todefine narrow mandrel elements 125A and a wide mandrel element 125B.Since the wide mandrel element 125B was formed from the implant region125M, it has different etch characteristics than the mandrel elements125A.

FIG. 4E illustrates the device 401 after several processes wereperformed. First, a spacer layer (e.g., silicon dioxide—not shown) wasformed above the mandrel elements and the hard mask layer 120. Then ananisotropic etch process was performed to remove portions of the spacerlayer formed on horizontal portions of the hard mask layers 120, 140 todefine spacers 150A, 150B on sidewalls of the mandrel elements 125A,125B, respectively. The remaining portions of the hard mask layer 140may be removed by tuning the etch chemistry during the spacer etch or bya subsequent etch process.

FIG. 4F illustrates the device 401 after an etch process was performedto remove the mandrel elements 125A selectively to the mandrel element125B. The spacers 150A define narrow mask elements, and the combinedmandrel element 125B/spacer 150B structure defines a wide mask element.

FIG. 4G illustrates the device 401 after several processes wereperformed to transfer the pattern defined by the spacers 150A, 150B andthe mandrel element 125B to the gate material layer 115. An etch processwas performed through the spacers 150A and the combined structure formedby the spacers 150B and the mandrel element 125B to pattern the hardmask layer 120. One or more etch processes were performed to remove thespacers 150A, 150B and the mandrel element 125B. An etch process wasperformed through the patterned hard mask layer 120 to pattern the gatematerial layer 115, defining short channel gate structures 1155 and along channel gate structure 115W.

The previous examples illustrate the patterning of a gate materiallayer. However, the application of these techniques is not limited tothe patterning of a particular layer. For example, the patterned layermay be an insulating layer, and the masks may be used to form trenchesin the dielectric layer for subsequently forming conductive interconnectfeatures (e.g., BEOL patterning). The techniques described herein allowshort channel and wide channel patterns to be formed using commonlithography processes and self-aligned etch processes. These processesreduce the likelihood of defects arising from pitch walkingmisalignment, etc.

The particular embodiments disclosed above are illustrative only, as theinvention may be modified and practiced in different but equivalentmanners apparent to those skilled in the art having the benefit of theteachings herein. For example, the process steps set forth above may beperformed in a different order. Furthermore, no limitations are intendedto the details of construction or design herein shown, other than asdescribed in the claims below. It is therefore evident that theparticular embodiments disclosed above may be altered or modi- fied andall such variations are considered within the scope and spirit of theinvention. Accordingly, the protection sought herein is as set forth inthe claims below.

What is claimed:
 1. A method, comprising: forming a first mandrel layerabove a first process layer; forming a first implant region in saidfirst mandrel layer; patterning said first mandrel layer to define aplurality of first mandrel elements, wherein at least a first subset ofsaid first mandrel elements is formed from said first mandrel layeroutside said first implant region and a second subset of said firstmandrel elements is formed from said first implant region; forming firstspacers on sidewalls of said plurality of first mandrel elements;selectively removing said first subset of said first mandrel elementswithout removing said second subset of said first mandrel elements; andpatterning said first process layer using said first spacers and saidsecond subset of said first mandrel elements as an etch mask.
 2. Themethod of claim 1, wherein said first process layer comprises a gatematerial layer, and patterning said gate material layer comprisesforming a first gate structure having a first critical dimension beneathone of said first spacers and forming a second gate structure having asecond critical dimension larger than said first critical dimensionbeneath a combined structure defined by one of said second subset ofsaid first mandrel elements and its associated first spacers.
 3. Themethod of claim 1, further comprising forming a first hard mask layerbetween said first process layer and said first mandrel layer, whereinpatterning said first process layer comprises performing a first etchprocess to transfer a pattern defined by said first spacers and saidsecond subset of said first mandrel elements to said first hard masklayer to define a patterned first hard mask layer and performing asecond etch process to etch said first process layer through saidpatterned first hard mask layer.
 4. The method of claim 3, furthercomprising removing said first spacers and said second subset of saidfirst mandrel elements prior to performing said second etch process. 5.The method of claim 1, wherein said first process layer comprises asecond mandrel layer, and the method further comprises: forming a secondprocess layer beneath said second mandrel layer; patterning said secondmandrel layer using said first spacers and said second subset of saidmandrel elements as an etch mask to define a second plurality of mandrelelements; forming second spacers on sidewalls of said plurality ofsecond mandrel elements; removing said second mandrel elements; andpatterning said second process layer using said second spacers as anetch mask.
 6. The method of claim 5, wherein said second process layercomprises a gate material layer, and patterning said gate material layercomprises forming gate structures having a first critical dimensionbeneath said second spacers, wherein a space is defined between firstand second subsets of said gate structures, said space having a widthcorresponding to a width of one of said second subset of said mandrelelements.
 7. The method of claim 5, further comprising forming a firsthard mask layer between said second mandrel layer and said secondprocess layer, wherein patterning said second process layer comprisesperforming a first etch process to transfer a pattern defined by saidsecond spacers to said first hard mask layer to define a patterned firsthard mask layer and performing a second etch process to etch said firstprocess layer through said patterned first hard mask layer.
 8. Themethod of claim 7, further comprising removing said second spacers priorto performing said second etch process.
 9. The method of claim 1,wherein said first process layer comprises a second mandrel layer, andthe method further comprises: forming a second process layer beneathsaid second mandrel layer; forming a second implant region in saidsecond mandrel layer; patterning said second mandrel layer using saidfirst spacers and said second subset of said first mandrel elements asan etch mask to define a plurality of second mandrel elements, whereinat least a first subset of said second mandrel elements is formed fromsaid second mandrel layer outside said second implant region and asecond subset of said second mandrel elements is formed from said secondimplant region; forming second spacers on sidewalls of said plurality ofsecond mandrel elements; selectively removing said first subset of saidsecond mandrel elements without removing said second subset of saidsecond mandrel elements; and patterning said second process layer usingsaid second spacers and said second subset of said second mandrelelements as an etch mask.
 10. The method of claim 9, wherein said secondprocess layer comprises a gate material layer, and patterning said gatematerial layer comprises forming gate structures having a first criticaldimension beneath said second spacers and forming a second gatestructure having a second critical dimension larger than said firstcritical dimension beneath a combined structure defined by one of saidsecond subset of said second mandrel elements and its associated secondspacers.
 11. The method of claim 9, further comprising forming a firsthard mask layer between said second mandrel layer and said secondprocess layer, wherein patterning said second process layer comprisesperforming a first etch process to transfer a pattern defined by saidsecond spacers and said second subset of said second mandrel elements tosaid first hard mask layer to define a patterned first hard mask layerand performing a second etch process to etch said first process layerthrough said patterned first hard mask layer.
 12. The method of claim11, further comprising removing said second spacers and said secondsubset of said second mandrel elements prior to performing said secondetch process.
 13. The method of claim 9, wherein forming said first andsecond implant regions comprises implanting boron into said first andsecond mandrel layers.
 14. The method of claim 13, wherein said firstand second implant regions are formed concurrently.
 15. The method ofclaim 13, wherein said first and second implant regions are verticallyaligned.
 16. The method of claim 1, wherein forming said first implantregion comprises implanting boron into said first mandrel layer.
 17. Amethod, comprising: forming a lower mandrel layer above a process layer;forming a lower implant region in said lower mandrel layer; forming anupper mandrel layer above said lower mandrel layer; forming an upperimplant region in said upper mandrel layer; patterning said uppermandrel layer to define a plurality of first mandrel elements, whereinat least a first subset of said first mandrel elements is formed fromsaid upper mandrel layer outside said upper implant region and a secondsubset of said upper mandrel elements is formed from said upper implantregion; forming first spacers on sidewalls of said plurality of uppermandrel elements; selectively removing said first subset of said uppermandrel elements without removing said second subset of said uppermandrel elements; patterning said lower mandrel layer using said firstspacers and said second subset of said upper mandrel elements as an etchmask to define a plurality of lower mandrel elements, wherein at least afirst subset of said lower mandrel elements is formed from said lowermandrel layer outside said lower implant region and a second subset ofsaid lower mandrel elements is formed from said lower implant region;forming second spacers on sidewalls of said plurality of lower mandrelelements; selectively removing said first subset of said lower mandrelelements without removing said second subset of said lower mandrelelements; and patterning said process layer using said second spacersand said second subset of said lower mandrel elements as an etch mask.18. The method of claim 17, wherein patterning said process layercomprises forming gate structures having a first critical dimensionbeneath said second spacers and forming a second gate structure having asecond critical dimension larger than said first critical dimensionbeneath a combined structure defined by one of said second subset ofsaid lower mandrel elements and its associated second spacers.
 19. Themethod of claim 17, wherein forming said upper and lower implant regionscomprises implanting boron into said upper and lower mandrel layers. 20.The method of claim 17, wherein said upper and lower implant regions arevertically aligned.